Indanomycin

A refined version of this reaction was used to obtain opticaliy active 3 from glycal 2. This product is readily converted to the tetrahydropyran 4, a subunit of the antibiotic indanomycin. 

Indanomycin has also been a target of the Boeckman group, which, while employing a quite different approach to the pyran nucleus, begins the route with a cuprate 1,2-addition to the readily available homo-chiral aldehyde (136). An excellent yield of two diastereomers (137) was obtained, epimeric at the carbon bearing the methyl group brou t in as part of the cuprate (equation 32). Thus, as confirmed by H NMR on the Mosher esters of (137), the stereoselectivity of the cuprate addition was >98%. 

Thus, (S,S)-tartaric acid (77) has been employed for constructing part of the structure of the antibiotic, indanomycin (ref.77). 

S,S)-Tartaric acid Indanomycin structure Multi-step 77... 

An early study of the allylation reactions of oxocarbenium systems has been described by Danishefsky for synthesis efforts directed towards indanomycin. The reactions of ( )-and (Z)-2-butenylsilanes silanes are the focus for this report. However, the study also examined reactions of the (E,Z)-mixture of 2-butenyl-tri-n-butylstannanes with tri-o-acetyl-o-galactal 132 at -30 °C, in the presence of BF3 OEt2... 

Scheme 13. Reductive lithiation in the total synthesis of indanomycin...

Most applications of the intramolecular Diels-Alder reaction use 1-substituted butadienes and these reactions often form a key step in the synthesis of polycyclic natural products. Substituents in the connecting chain may influence the facial selectivity of the cycloaddition reaction, as well as the endo. exo selectivity. For example, in a synthesis of the antibiotic indanomycin, the triene 83 gave, on heating. 

Indanomycin (X-14547 A) [S. antibioticus] 493.69 ethyl acetate, methanol ionophore particularly for K but Rb and Cs are transported across the membrane as well binding mono-, di-, and trivalent cations... 

Other natural products has been made only within the past few years. Consequently, it has not yet been widely utilized. Although more circuitous, Protocols II and IV have been more widely exploited in the synthesis of a variety of natural products, such as rapamycin, caUculin indanomycin, sangUfehrin vitamin restrictinol, ... 

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